Lymphoid interstitial pneumonitis (LIP) and diffuse infiltrative lymphocytosis syndrome (DILS) are HIV-related disorders associated with improved survival. An important feature which these two conditions share in common is marked infiltration of the lungs by CD8+t lymphocytes. A condition similar to LIP and DILS occurs in a substantial fraction of macaques experimentally inoculated with certain strains of simian immunodeficiency virus (SIV). Macaques with this condition also have an improved survival time. It is proposed to employ the SIV/macaque model of LIP/DILS to test the hypothesis that the pulmonary cell-mediated immune response in these conditions provide systemic immunologic benefit and retard disease progression. (End of Abstract)